Escape the nodeValue with htmlspecialchars()

Fixes ISLANDORA-879 :
  https://jira.duraspace.org/browse/ISLANDORA-879
Fix for Notice.

Notice: Undefined index: #autocomplete_path in theme_textfield()
(line 3821 of /Users/peter/reposervice/drupal/includes/form.inc).

As discovered by Peter on google groups:

https://groups.google.com/forum/?fromgroups=#!topic/islandora-dev/9vH6jEXuYtM
Merge remote-tracking branch 'nigelgbanks/7.x-fix-for-autocomplete-notice' into lyr-master

Fixes "Notice: Undefined index: \#autocomplete_path in theme_textfield()"
https://github.com/nigelgbanks/islandora_xml_forms/commit/05bc4d06d90b0c795b4f06bf4f0da8989146582d
Merge pull request #97 from nigelgbanks/7.x-fix-for-autocomplete-notice

Fix for Notice Notice: Undefined index: #autocomplete_path in theme_textfield() (line 3821 of /Users/peter/reposervice/drupal/includes/form.inc).
Merge pull request #96 from lyrasis/lyr-master

Escape the nodeValue with htmlspecialchars()
Remove the content model autocomplete away from islandora_xml_forms.
Merge pull request #98 from jordandukart/7.x-remove-autocomplete

Remove the content model autocomplete away from islandora_xml_forms.